Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent can support and/or reinforce the vessel walls while maintaining the vessel in an open, unobstructed condition.
Stents may be used in a wide variety of locations in the body including in coronary arteries, renal arteries, peripheral arteries including iliac arteries, arteries of the neck and cerebral arteries. Stents are also used in other bodily locations including but not limited to arteries, veins, biliary ducts, urethras, fallopian tubes, bronchial tubes, the trachea, the esophagus and the prostate.
Stents typically are self-expanding, balloon expandable or a hybrid of the two. Self-expanding stents may be made of shape memory metals such as nitinol, shape memory polymer materials, or constructed of non-shape memory metals but of a design which exhibits self-expansion characteristics. Balloon expandable stents are typically delivered on a balloon and the balloon is used to expand the stent. Hybrid stents may have both self-expanding properties and balloon expanding properties.
Typically, stents are delivered to desired bodily locations via the use of catheters. A catheter comprising a stent is introduced into a bodily vessel and advanced through the vasculature in the body until the stent is positioned in a desired location. Often, the stent can be protected by a retractable sheath which is disposed about the stent and which increases the profile of the delivery catheter. The sheath may be removed from about the stent via the use of a retraction device such as a pull-wire, pull rod or a catheter tube which is connected to the sheath. As part of the removal, the sheath may optionally be rolled off of the stent. In the case of self-expanding stents, the sheath may also restrain the stent from self-expanding. Once at the desired location, the stent is either allowed to self-expand and/or balloon expanded. In the case of self-expanding stents, the self-expansion may occur as a result of the removal of the sheath from about the stent.
Some stent delivery and deployment assemblies are known which utilize restraining sleeves that overlie one or more portions of the stent prior to delivery. U.S. Pat. No. 4,950,227 to Savin et al, relates to an expandable stent delivery system in which a sleeve overlaps the distal or proximal margin (or both) of the stent during delivery. That patent discloses a stent delivery system in which a catheter carries, on its distal end portion, a stent which is held in place around the catheter prior to and during percutaneous delivery by means of one and preferably two sleeves. The sleeves are positioned around the catheter with one end portion attached thereto and overlap an end portion(s) of the stent to hold it in place on the catheter in a contracted condition. The stent is expandable by means of the expandable balloon on the catheter. During expansion of the stent at the deployment site, the stent margins are freed of the protective sleeve(s). U.S. Pat. No. 5,403,341 to Solar, relates to a stent delivery and deployment assembly which uses retaining sheaths positioned about opposite ends of the compressed stent. The retaining sheaths of Solar are adapted to tear under pressure as the stent is radially expanded, thus releasing the stent from engagement with the sheaths. U.S. Pat. No. 5,108,416 to Ryan et al., describes a stent introducer system which uses one or two flexible end caps and an annular socket surrounding the balloon to position the stent during introduction to the deployment site.
Copending U.S. patent application Ser. No. 09/407,836 which was filed on Sep. 28, 1999 and entitled Stent Securement Sleeves and Optional Coatings and Methods of Use , and which is incorporated in its entirety herein by reference, provides for a stent delivery system having sleeves. In U.S. Ser. No. 09/407,836 the sleeves may be made up of a combination of polytetrafluoroethylene (PTFE) as well as one or more thermoplastic elastomers.
In many cases a catheter system employing one or more stent retaining sheath or sleeve will require a pull-back member and an associated pull back mechanism for drawing the sheath or sleeve off of the stent prior to stent delivery. Such pull back members may be bulky and undesirably increase the profile and/or complexity of the catheter system and its use. Many catheter systems employ pull back mechanisms which fold the sheath or sleeve over itself, thus undesirably increasing the profile of the catheter prior to withdrawal of the catheter. In the case of systems employing self-retracting sleeves or socks, the self-retracting sleeves may also be configured to fold over during retraction. Because folding of sheathes, sleeves or socks may be difficult or undesirable in the restrictive confines of a body lumen it would be desirable to provide a stent retaining device which is both self-retracting and which does not rely on a folding principle to retract off of the stent.
The entire content of all of the patents listed within the present patent application are incorporated herein by reference.
Without limiting the scope of the invention a brief summary of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.